1. Field of the Invention
The present invention relates to an apparatus for automatically changing a robot tool tip member, which operates in the condition that the tool tip member is threadedly mounted on a tool body which is, in turn, mounted on a robot arm. For example, the present invention is applied to an apparatus for automatically changing a tool tip member mounted on a distal end of a tool body for arc welding or laser machining.
2. Description of the Related Art
When an industrial robot (hereinafter simply referred to as a “robot”) is used for arc welding or laser machining, a tool tip member is mounted on a distal end of a tool body. Typically, the tool tip member is mounted by threadedly engaging it with the tool body.
As the tool tip member is used repeatedly, it wears and must, eventually, be changed. Therefore, in order to increase an efficiency of labor savings achieved by robots, various techniques for automatically changing tool tip members have been developed and proposed.
For example, Japanese Unexamined Patent Publication (Kokai) No. 10-43879 discloses a method for automatically demounting or mounting a nozzle tip (a tool tip member used for laser machining) from or on a distal end of a laser machining head (a tool body) in a three-dimensional laser machining apparatus using a robot. In this method, the nozzle tip is held by a nozzle tip holding device provided with a power chuck, and the nozzle tip is demounted or mounted by rotating the machining head, on which the nozzle tip is mounted (or on which the nozzle tip is to be mounted), about a center axis of the nozzle tip with the help of five-axis control function of the laser machining apparatus. Further, among motors that are used in the laser machining apparatus for driving a wrist portion of the robot, motors for controlling two-axes of the wrist are contained in the rear of the wrist portion, and power transmission means such as drive shafts are used for securing an operation range of the wrist.
However, when a dedicated automatic changing apparatus for demounting or mounting a tool tip member is used in the method described above, the automatic changing apparatus requires a driving power source to drive actuators used for fastening the tool tip member, resulting in a problem that running costs are increased.
Further, when the robot of the laser machining apparatus is used for such purpose, the tool tip member must be rotated for threadedly mounting or demounting the tool tip member on or from the tool body, so that the robot is required to rotate continuously about the central axis of the rotational operation.
However, in a typical robot system for performing arc welding or laser machining, as the robot itself has various lines (wirings, tubings and pipings) attached thereto, such as a motor control line, an energy supply line for a tool body, a sensor signal line, an assist gas supply line and the like, the operation range of the wrist axis of the robot is restricted by these lines and, therefore, the continuous rotation required for threadedly mounting or demounting the tool tip member on or from the tool body is not permitted in most cases.
For example, regarding the line for supplying assist gas to the machining head, it is apparent that the line arrangement wherein the lines are attached to the outside of the apparatus is incompatible with the requirement of continuous rotation described above. Further, as can be seen in the example of the Japanese Unexamined Patent Publication (Kokai) No. 10-43879 mentioned above, a dedicated mechanism for securing the operation range of the wrist portion has been required.